Miniaturized imaging module construction technique

ABSTRACT

A method of constructing an image reader module and the image reader are described. The image reader module includes two or more circuit boards in a stacked configuration. Corresponding notches for receiving supports are formed along adjacent edges of the boards, which also have electrical contact points at the edges of each board connected to circuits on the boards. The supports are mounted in the notches between the two or more circuit boards to structurally interconnect the boards. Each of the supports, which may be flex cables or conductive bus bars, have one or more electrical conductors that are electrically connected to the contact points on the boards to electrically interconnect the boards, whereby the connections between the electrical conductors and the contact points form test points for the module. The notches may be substantially rectangular to receive the flex cable or may be slots to receive a bus bar. One end of the structural support flex cable or bus bar may be flush with one of the circuit boards and the other end of the structural support may extend past another one of the circuit boards. The supports may be soldered to the edges of the boards within the notches, which may be initially plated. In the image reader module an image sensor may be located on one of the circuit boards and an illumination assembly may be located on another of the circuit boards.

FIELD OF INVENTION

The present invention relates generally to miniaturized image readermodules and more specifically to a packaging technique for use in aminiaturized image reader module.

BACKGROUND OF THE INVENTION

There exists a need in the industry for reduced area image readingdevices that can be used in industrial application including bar codereaders, PDA's and even wireless/cellular picture phones. With theever-decreasing size of these applications, miniaturization of the imagereading module itself is a perennial problem.

Present packaging techniques are often not adequate for the rate ofminiaturization currently required in the industry. Another problem withcurrent packaging techniques is a lack of a suitable device testingpoints, which could be used instead of the device's interconnect ribbonsat the verification and calibration stage of the manufacturing process.These ribbons become worn and often need replacing before finalshipping.

US Patent Application Publication 2003/0089776 filed on Mar. 7, 2002 byHenick and published on May 15, 2003, discloses a packaging techniquefor an image reader module, which uses support posts to connect theboards and provide structural integrity. These posts may also be usedfor electrical connectivity between the boards. The main drawback tothis technique however, is that the posts pass directly throughapertures within the boards, taking up valuable real estate within themodule. Further, this structure does not include test points useful intesting the module at the manufacturing stage.

Another prior art technique for interconnecting circuit boards in avariety of modules, involves the use of connector rods attached tocutout grooves in the boards. The rods are mounted perpendicularlybetween two boards to form bridges. The rods fit into the cutout groovesand are soldered into place. These rods provide structural integrity aswell as electrical connectivity. In a camera module however, the use ofthis technique to include test pads at the solder joints or test padsthat are electrically connected to the solder joints is not disclosed.

There are packaging techniques which use flex cables to connect circuitboards in an image reader module. The flex cables are connected to theouter edges of the boards then folded to make the boards parallel toeach other for packaging. The main drawback to this technique is theamount of flex cable that is required, and the wear and tear that isimparted on the cables when they are folded over. Further, the cables donot provide any structural integrity to the boards. The structuralsupport must be provided in other ways such as the housing or supportposts. A further disadvantage is the space that the folded cable takesup in the module. With ever decreasing module sizes, this can be asignificant drawback.

Therefore there is a need for a packaging technique which allows for theneeded level of miniaturization required by the industry, whileproviding test points electrically connected to the circuit boardsuseful in the verification and product testing stages of themanufacturing process.

SUMMARY OF THE INVENTION

It is an advantage of the present invention to provide a packagingtechnique that permits the needed level of miniaturization required bythe industry.

It is a further advantage of the present invention to provide apackaging technique that provides test points electrically connected tothe circuit board.

The present invention is directed to an image reader module comprisingtwo or more circuit boards in a stacked configuration The boards havecorresponding notches along adjacent edges and electrical contact pointsat the edges of each board connected to circuits on the board. Supportsare mounted in the notches between the two or more circuit boards tostructurally interconnect the boards. Each of the supports have one ormore electrical conductors that are electrically connected to thecontact points on the boards to electrically interconnect the boards,whereby the connections between the electrical conductors and thecontact points form test points for the module.

In accordance with a further aspect of the invention, the support is aflex cable having ends adapted to fit securely within the notches, whichare substantially rectangular, the flex cable may have a width greaterthen the notches.

In accordance with another aspect of the invention, the notches aresubstantially in the shape of a slot and the support is a bus bar havingends adapted to fit securely within the slot shaped notches in thecircuit boards.

In accordance with a further aspect of the invention, one end of thesupport flex cable or bus bar is flush with one of the circuit boardsand the other end of the support extends past another one of the circuitboards.

In accordance with a specific aspect of the invention, the support issoldered within the corresponding notches of the circuit boards.

The present invention is further directed to a method of constructing animage reader module having two or more circuit boards in a stackedconfiguration, each board having electrical contact points at the edgeof the board surface connected to circuits on the board. The methodcomprises forming corresponding notches at predetermined locations alongadjacent edges of the circuit boards and mounting supports havingstructural support properties in the corresponding notches between thecircuit boards to provide structural support between the boards, whereinthe supports are flex cables having electrical conductors or conductivebus bars. Further, the method includes connecting the electricalconductors to the contact points for electrically interconnecting theboards, whereby the connections between the electrical conductors andthe contact points form test points.

In accordance with a further aspect of this invention, the methodincludes cutting lengths of the supports substantially equal to orgreater then a desired spacing between the stacked circuit boards.

In accordance with a specific aspect of the invention, the notches mayhave a substantially rectangular shape to receive a flex cable supportor may be a slot to receive a conductive bus bar support.

In accordance with another specific aspect of the invention, the supportis soldered to the corresponding notches at the edge of the circuitboards, wherein the edges may be initially plated.

In accordance with another aspect of the invention, the image readermodule may have an image sensor on one of the circuit boards and anillumination assembly on another of the circuit boards.

Other aspects and advantages of the invention, as well as the structureand operation of various embodiments of the invention, will becomeapparent to those ordinarily skilled in the art upon review of thefollowing description of the invention in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein:

FIG. 1A is a top view of a portion of a circuit board and the connectionassembly in accordance with the present invention;

FIG. 1B is a side schematic view of one embodiment of an image readermodule in accordance with the present invention;

FIG. 1C is a view of a section of flex cable for use with the presentinvention;

FIG. 1D is a side schematic view of another embodiment of an imagereader module in accordance with the present invention;

FIGS. 2A and 2B are side and top schematic views of a further embodimentof an image reader module in accordance with the present invention; and

FIG. 3 is a view of the connection between a bus bar and a circuitboard.

DETAILED DESCRIPTION

Packaging is an ongoing problem for miniature image readers, which mustfit into increasingly smaller spaces in imaging devices such as bar codereaders, PDA's and even wireless/cellular picture phones. These smallersized components cannot use known packaging technologies such asstandard Board-to-Board (BTB) connectors. Successful packaging of animage reader module requires care in interconnecting the circuit boardswhile maintaining structural stability and electrical connectivity.

Generally, an image reader module is made up of two or more circuitboards including at least an image sensor board and an illuminationboard. An objective lens usually housed in a barrel is positioned overthe sensor board at a fixed distance dependent on the required focallength. The illumination board may be positioned over the image sensorboard and may contain an aperture to accommodate the objective lensbarrel. Electrical connectivity between boards is usually in the form ofa ribbon cable and connectors, or may include posts that run through theboards.

Details of the packaging techniques of the present invention will now bedescribed with reference to the accompanying drawings.

Referring now to FIGS. 1A and 1B, which illustrate one embodiment of thepresent invention, corresponding notched spaces 20 are cut out of theadjacent edges of the boards 10, 50, for receiving flex cables 30, whichare mounted between the boards 10, 50. The flex cables would be of atype well known in the art, which contain a number of individualconductive paths in the form of conductors separated by insulatingmaterial.

The cables 30 are formed into substantially rectangular shapes of a sizeto fit into the notched spaces 20. In a bar code reader module, theseboards include an image sensor board 10 and an illumination board 50 forexample. The notches 20 on the edges of the boards 10, 50 may begenerally rectangular with a further circular cutout 25 in each corner,though the notches 20 need not be identical. Solder 45 is applied toconnect the flex cable 30 to the boards 10, 50 at the contacts 40 suchthat a conductive path is formed only between the individual cableswithin the flex cable 30 and the individual contacts 40 on the boards10, 50.

Those skilled in the art would understand that the flex cable would befabricated or modified to provide this conductive path between the cable30 and the contacts 40. This may entail stripping some of the insulatingmaterial away to expose the wires. The circular cut-out portion 25 ofthe notches 20 on the boards may be plated 55 to provide low impedanceshielding and structural strength to the cable 30 where soldered inplace. The plating 55 may be extended to encompass a portion of thelands on the circuit boards 10, 50.

The flex cables 30 are shaped to fit tightly into the notches 20 at aperpendicular angle such that the cables 30 form bridges between atleast two boards 10, 50. When soldered into place, the cable 30 provideselectrical connectivity and structural support between the boards 10,50. Each cable 30 edge is soldered to the boards 10, 50 at the circularcutout portion 25 of the notch 20 on each board 10, 50.

A plurality of electrical contacts 40 located at the notches, may beused to supply power and ground, or other electrical signals, to theboards 10, 50. An application of solder 45 electrically connects theflex cable 30 to the board 10 at the metal plating 55 and subsequentlyto the electrical contacts 40 with very little impedance. The solderedcontacts 40 may also provide the connectivity of the data signalsbetween the cable 30 and the boards 10, 50. Further, the connectionsbetween the flex cable 30 conductors and the contacts 40 may form testpoints or pads for use as access points for product testing andverification at the manufacturing stage.

It should be noted by those skilled in the art that different patternsor shapes of the connecting flex cables 30 may be used, and differentlyshaped notches on the boards 10, 50 may also be used while remainingwithin the scope of the present invention. For example, as shown in FIG.1C the corners of the flex cable 30 may be cut out such that the portionof the cable 30 which fits into the notch 20 is narrower than theportion of the flex cable 30 that fits between the boards 10, 50. Withthis shape of cable 30, the wider portion provides extra structuralsupport to the boards 10, 50 by providing a “shelf” like structure 35,on which the board 10, 50 edges can rest.

In another embodiment of the present invention illustrated in FIG. 1D,the flex cable 30, at either the top or bottom edge, may extend slightlypast the edge of the board 10 or 50, to form a type of edge connector110. This edge connector 110 may be used to connect to other modules orto boards such as a companion processor board or it may be used toconnect to testing equipment to verify device performance.

In a further embodiment of the present invention shown in FIGS. 2A and2B, holes are drilled close to the edge of the board 10, and theremaining edge material is cut away to leave notches 60 in the shape ofa slot with a rounded end at the edge of the boards 10, 50. Interconnectbus bars 100 fit into the notches 60 at a perpendicular angle to theboards 10, 50. The notches 60 allow the bus bars 100 to remain entirelywithin the packaging dimensions. The open end of these notches 60permits easy access for soldering, either manual or automated. Thenotches 60 may be plated 90 to provide a low impedance connection to theinterconnect bus bar 100 when it is soldered in place. Further, theplating 90 of the notch 60 can extend to encompass the entire notch 60as well as a portion of the lands on the circuit boards 10, 50.

With reference to FIG. 3, the plating 90 of the notch 60 may be securedto the board 10, 50 for added strength. This is done by forming smallholes 70 in board 10, 50. The metal used in the plating 90 process maybe heated and applied to the board 10 in molten form. The molten metalseeps into the small holes 70 in the board 10, 50 thereby anchoring theplating 90 to provide extra stability to the plated area 90. The bus bar100, shown in top view, is seated within the notch 60. Solder 45connects the bus bar 100 to the board 10 at the metal plating 90 andsubsequently to an electrical contact 40 on the board 10, 50 with verylittle impedance. Further, the connections between the bus bars 100 andthe contacts 40 may form test points or pads for use as access pointsfor product testing and verification at the manufacturing stage.

The resulting wire frame provides structural support for the module aswell as electrical connectivity between the boards 10, 50. Any number ofelectrical connections can be made between boards 10, 50 with thistechnique. It should be noted that various patterns of bus bar 100interconnections and different quantities of bus bars 100 could also beused to increase structural strength without departing from the scope ofthe present invention.

As is clear from the above, the present invention has the advantage thatit provides a packaging technique that integrates smaller components andboards in an image reader module so as to enable the module to fit intoa compact housing and at the same time, it provides for a device havingmechanical support as well as electrical connectivity between the imagesensor board and the illumination board.

The testing points described in the above embodiments may be used totest and calibrate the device during the manufacturing stage, such thattest probes or connectors, either hand held or fixed, may be usedinstead of the normally fragile interconnection ribbons, which becomeworn very quickly. This wear can include damage to the delicateinterconnect contacts or to the ribbon cable itself which is quite thinand may break easily if folded or bent excessively. Further, worncontacts can cause short circuits in the connector that can then damageelectronic circuitry. Once the ribbons are worn, they must be replacedwith a new ribbon, which, depending on the extent of the testing, mayalso need replacing before the product is ready for shipping. With theuse of the testing points, the ribbons need only be connected at thefinal stage of the module assembly.

While the invention has been described according to what is presentlyconsidered to be the most practical and preferred embodiments, it mustbe understood that the invention is not limited to the disclosedembodiments. Those ordinarily skilled in the art will understand thatvarious modifications and equivalent structures and functions may bemade without departing from the spirit and scope of the invention asdefined in the claims. Therefore, the invention as defined in the claimsmust be accorded the broadest possible interpretation so as to encompassall such modifications and equivalent structures and functions.

1-29. (canceled)
 30. An image reader module comprising: two or morecircuit boards in a stacked configuration, the circuit boards havingcorresponding notches along adjacent edges and electrical contact pointsat the edge of the board surfaces connected to circuits on the board;structural supports mounted in the corresponding notches between thecircuit boards and adapted to fit within the corresponding notches inthe circuit boards to provide structural support between the boards,wherein at least one of the supports is a flex cable adapted to fitsecurely within the corresponding notches in the circuit boards, theflex cable comprising a plurality of electrical conductors, theelectrical conductors being electrically connected to a plurality ofcontact points on each of the boards for electrically interconnectingthe boards, and at least one end of the flex cable extending past one ofthe circuit boards, whereby the electrical connections between theelectrical conductors of the flex cable and the contact points formrespective test points for a test probe or connector in testing at leastpart of the image reader at a manufacturing process.
 31. The imagereader module of claim 30 wherein one of the circuit boards houses animage sensor.
 32. The image reader module of claim 31 wherein another ofthe circuit boards houses an illumination assembly.
 33. The image readermodule of claim 30, wherein the notches are substantially rectangular.34. The image reader module of claim 30, wherein the flex cable includesa section having a width greater then the notches.
 35. The image readermodule of claim 30, wherein the flex cable is adapted to fit securelywithin the corresponding notches in the circuit boards, with the one endof the flex cable extending past the one of the circuit boards and theother end of the flex cable flush with another one of the circuitboards.
 36. The image reader module of claim 30, wherein the flex cableis soldered within the corresponding notches of the circuit boards. 37.The image reader module of claim 30, wherein the notches aresubstantially in the shape of a slot.
 38. The image reader module ofclaim 37, wherein one of the supports is a bus bar having ends adaptedto fit securely within the notches in the circuit boards and havingelectrical connections with the circuit boards through the contactpoints.
 39. The image reader module of claim 37, wherein at least one ofthe supports is a bus bar adapted to fit securely within the notches inthe circuit boards and having electrical connections with the circuitboards through the contact points, with one end of the bus bar beingflush with one of the circuit boards and the other end of the bus barextending past another one of the circuit boards.
 40. The image readermodule of claim 38, wherein the bus bar is soldered within thecorresponding notches of the circuit boards.
 41. A method ofconstructing an image reader module having two or more circuit boards ina stacked configuration, each board having a plurality of electricalcontact points at the edge of the board surface connected to circuits onthe board, comprising: forming corresponding notches along adjacentedges of the circuit boards; mounting structural supports in thecorresponding notches between the circuit boards, the structuralsupports being adapted to fit within the corresponding notches in thecircuit boards to provide structural support between the circuit boards;wherein at least one of the structural supports is a flex cable adaptedto fit securely within the corresponding notches in the circuit boards,the flex cable comprising a plurality of electrical conductors, with atleast one end of the flex cable extending past one of the circuitboards, and the method further comprising connecting the plurality ofelectrical conductors of the flex cable to the contact points toelectrically interconnect the circuit boards, whereby the electricalconnections between the electrical conductors of the flex cable and thecontact points form respective test points for a test probe or connectorin testing at least part of the image reader at a manufacturing process.42. A method as claimed in claim 41, wherein the step of connectingcomprises connecting the flex cable to the circuit boards such that oneend of the flex cable extends past the one of the circuit boards and theother end of the flex cable is flush with another one of the circuitboards.
 43. A method as claimed in claim 42, further comprising: cuttinglengths of the flex cable substantially equal to a desired spacingbetween the stacked circuit boards.
 44. A method as claimed in claim 42,further comprising: cutting lengths of the flex cable greater then adesired spacing between the stacked circuit boards.
 45. A method asclaimed in claim 42, wherein circuit board notching includes cutting thenotches in a substantially rectangular shape.
 46. A method as claimed inclaim 42, further comprising: soldering the flex cable to the edge ofeach circuit board in the notch.
 47. A method as claimed in claim 42,further comprising: plating the edge of the circuit board within thenotches.
 48. A method as claimed in claim 42, further comprising:soldering the flex cable conductors to the circuit board contacts.
 49. Amethod as claimed in claim 41, wherein at least one of the structuralsupports is a conductive bus bar having structural support properties inthe corresponding notches between the circuit boards, the bus bar beingadapted to fit within the corresponding notches in the circuit boards,and wherein the step of connecting comprises connecting the bus bar tothe contact points to electrically interconnect the circuit boards,whereby the connection between the bus bar and the contact point formthe test point.
 50. A method as claimed in claim 49, further comprising:cutting lengths of the bus bar substantially equal to a desired spacingbetween the circuit boards.
 51. A method as claimed in claim 49, furthercomprising: cutting lengths of the bus bar greater then a desiredspacing between the circuit boards.
 52. A method as claimed in claim 49,wherein circuit board notching includes: cutting the notches as a slotwith a rounded end.
 53. A method as claimed in claim 52, furthercomprising: soldering the bus bar to the edge of each circuit boardwithin the slot.
 54. A method as claimed in claim 52, furthercomprising: plating the edge of the circuit board within the slot.
 55. Amethod as claimed in claim 52, further comprising: soldering the busbars to the circuit board contacts.